The purpose of this thesis is to analyze the success factors of ERP system in corporations and to know what is different in the factors depending on organizational culture and size. Considering there are various results from introduction of the same information technology(IT), it is implied that organizational characteristics make a difference. In this thesis we did factor analysis and multiple regression about the factors based on the previous studies and analyzed the priorities depending on organizational culture and size. The results show that mechanistic organization has key success factors of work process change, project team abilities, and determination of CEO while organic organization has those of work process change and project team abilities. Plus bigger sized organization has success factors of work process change, project team abilities, and determination of CEO while small sized organization has those of work process change and project team abilities.